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Home › Buick › 2002 › Century Custom › Repair and Diagnosis › Engine Performance › System › Engine Control System Self-Diagnostics - 3.1L Engine › Diagnostic Tests › DTC P0135: Ho2S Heater Performance › Diagnostic Procedures

Diagnostic Procedures

  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Allow the engine to idle at operating temperature. Monitor the HO2S 1 Heater Current parameter on a scan tool. Allow the current to stabilize. Is HO2S 1 heater current within 0.25-0.85 A? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See CONDITIONS FOR RUNNING DTC . Does the DTC fail this ignition? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
    NOTE: Use a known-good ground. Do not use the HO2S 1 heater low control circuit or low reference circuit.
  4. Disconnect HO2S 1 harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S 1 harness connector heater ignition voltage circuit. Does test light illuminate? If yes, go to step  6. If no, go to next step.
  5. Check HO2S 1 heater ignition voltage fuse. Is fuse open? If yes, go to step  11. If no, go to step  12.
  6. Turn ignition off. Connect a test light between the HO2S 1 ignition 1 voltage circuit and heater low control circuit. Start engine. Does test light illuminate? If yes, go to next step. If no, go to step  8.
  7. Leave the test light connected between HO2S 1 heater ignition voltage circuit and heater low control circuit. Turn ignition off. Turn ignition on, with engine off. Does the test light illuminate? If yes, go to step  9. If no, go to step  13.
  8. Turn ignition off. Disconnect the PCM connector containing the HO2S 1 heater low control circuit. Using DMM, measure resistance of HO2S heater low control circuit between PCM harness connector and HO2S harness connector. Is resistance within 0-5 ohms? If yes, go to step  15. If no, go to step  10.
  9. Check HO2S 1 heater low control circuit for a short to ground. Did you find and correct the condition? If yes, go to step  18. If no, go to step  15.
  10. Check HO2S 1 heater low control circuit for an open or high resistance condition. Did you find and correct the condition? If yes, go to step  18. If no, go to step  15.
  11. Check HO2S 1 heater ignition voltage circuit for a short to ground. Replace fuse. Did you find and correct the condition? If yes, go to step  18. If no, go to step  15.
  12. Check HO2S 1 heater ignition voltage circuit for an open or high resistance condition. Did you find and correct the condition? If yes, go to step  18. If no, go to step  15.
  13. At the disconnected HO2S 1 pigtail connector, test the HO2S heater ignition voltage circuit for continuity between the following circuits of the HO2S: The HO2S 1 high signal, HO2S 1 low signal, HO2S 1 outer shell or a good ground. Do any of the circuits measure other than infinite resistance? If yes, go to step  16. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  14. Inspect for poor connections at the harness connector of the HO2S 1. Did you find and correct the condition? If yes, go to step  18. If no, go to next step.
  15. Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  18, If no, go to step  17.
  16. Replace the HO2S 1. After repairs, go to step  18
  17. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  18. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  19. Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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